diff --git a/polygerrit-ui/app/elements/core/gr-reporting/gr-jank-detector.js b/polygerrit-ui/app/elements/core/gr-reporting/gr-jank-detector.js
new file mode 100644
index 0000000..28c46f4
--- /dev/null
+++ b/polygerrit-ui/app/elements/core/gr-reporting/gr-jank-detector.js
@@ -0,0 +1,61 @@
+/**
+ * @license
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+(function() {
+  'use strict';
+
+  const JANK_SLEEP_TIME_MS = 1000;
+
+  const GrJankDetector = {
+    // Slowdowns counter.
+    jank: 0,
+    fps: 0,
+    _lastFrameTime: 0,
+
+    start() {
+      this._requestAnimationFrame(this._detect.bind(this));
+    },
+
+    _requestAnimationFrame(callback) {
+      window.requestAnimationFrame(callback);
+    },
+
+    _detect(now) {
+      if (this._lastFrameTime === 0) {
+        this._lastFrameTime = now;
+        this.fps = 0;
+        this._requestAnimationFrame(this._detect.bind(this));
+        return;
+      }
+      const fpsNow = 1000/(now - this._lastFrameTime);
+      this._lastFrameTime = now;
+      // Calculate moving average within last 3 measurements.
+      this.fps = this.fps === 0 ? fpsNow : ((this.fps * 2 + fpsNow) / 3);
+      if (this.fps > 10) {
+        this._requestAnimationFrame(this._detect.bind(this));
+      } else {
+        this.jank++;
+        console.warn('JANK', this.jank);
+        this._lastFrameTime = 0;
+        window.setTimeout(
+            () => this._requestAnimationFrame(this._detect.bind(this)),
+            JANK_SLEEP_TIME_MS);
+      }
+    },
+  };
+
+  window.GrJankDetector = GrJankDetector;
+})();
diff --git a/polygerrit-ui/app/elements/core/gr-reporting/gr-jank-detector_test.html b/polygerrit-ui/app/elements/core/gr-reporting/gr-jank-detector_test.html
new file mode 100644
index 0000000..6faeec1
--- /dev/null
+++ b/polygerrit-ui/app/elements/core/gr-reporting/gr-jank-detector_test.html
@@ -0,0 +1,78 @@
+<!DOCTYPE html>
+<!--
+@license
+Copyright (C) 2018 The Android Open Source Project
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+<meta name="viewport" content="width=device-width, minimum-scale=1.0, initial-scale=1.0, user-scalable=yes">
+<title>gr-jank-detector</title>
+
+<script src="../../../bower_components/webcomponentsjs/webcomponents-lite.min.js"></script>
+<script src="../../../bower_components/web-component-tester/browser.js"></script>
+<link rel="import" href="../../../test/common-test-setup.html"/>
+
+<script src="gr-jank-detector.js"></script>
+
+<script>
+  suite('gr-jank-detector tests', () => {
+    let sandbox;
+    let clock;
+    let instance;
+
+    const NOW_TIME = 100;
+
+    setup(() => {
+      sandbox = sinon.sandbox.create();
+      clock = sinon.useFakeTimers(NOW_TIME);
+      instance = GrJankDetector;
+      instance._lastFrameTime = 0;
+      sandbox.stub(instance, '_requestAnimationFrame');
+    });
+
+    teardown(() => {
+      sandbox.restore();
+    });
+
+    test('start() installs frame callback', () => {
+      sandbox.stub(instance, '_detect');
+      instance._requestAnimationFrame.callsArg(0);
+      instance.start();
+      assert.isTrue(instance._detect.calledOnce);
+    });
+
+    test('measures fps', () => {
+      instance._detect(10);
+      instance._detect(30);
+      assert.equal(instance.fps, 50);
+    });
+
+    test('detects jank', () => {
+      let now = 10;
+      instance._detect(now);
+      const fastFrame = () => instance._detect(now += 20);
+      const slowFrame = () => instance._detect(now += 300);
+      fastFrame();
+      assert.equal(instance.jank, 0);
+      _.times(4, slowFrame);
+      assert.equal(instance.jank, 0);
+      instance._requestAnimationFrame.reset();
+      slowFrame();
+      assert.equal(instance.jank, 1);
+      assert.isFalse(instance._requestAnimationFrame.called);
+      clock.tick(1000);
+      assert.isTrue(instance._requestAnimationFrame.called);
+    });
+  });
+</script>
diff --git a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.html b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.html
index 2970a26..cbb2c09 100644
--- a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.html
+++ b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.html
@@ -19,5 +19,6 @@
 <link rel="import" href="../../shared/gr-js-api-interface/gr-js-api-interface.html">
 
 <dom-module id="gr-reporting">
+  <script src="gr-jank-detector.js"></script>
   <script src="gr-reporting.js"></script>
 </dom-module>
diff --git a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js
index 0db442f..ae67dac 100644
--- a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js
+++ b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting.js
@@ -48,6 +48,14 @@
     STARTED_HIDDEN: 'hidden',
   };
 
+  // Frame rate related constants.
+  const JANK = {
+    TYPE: 'lifecycle',
+    CATEGORY: 'UI Latency',
+    // Reported events - alphabetize below.
+    COUNT: 'Jank count',
+  };
+
   // Navigation reporting constants.
   const NAVIGATION = {
     TYPE: 'nav-report',
@@ -118,6 +126,8 @@
   };
   catchErrors();
 
+  GrJankDetector.start();
+
   const GrReporting = Polymer({
     is: 'gr-reporting',
 
@@ -206,6 +216,11 @@
     },
 
     beforeLocationChanged() {
+      if (GrJankDetector.jank > 0) {
+        this.reporter(
+            JANK.TYPE, JANK.CATEGORY, JANK.COUNT, GrJankDetector.jank);
+        GrJankDetector.jank = 0;
+      }
       for (const prop of Object.keys(this._baselines)) {
         delete this._baselines[prop];
       }
diff --git a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html
index bfb45f6..e2bb83d 100644
--- a/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html
+++ b/polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html
@@ -93,7 +93,11 @@
     test('beforeLocationChanged', () => {
       element._baselines['garbage'] = 'monster';
       sandbox.stub(element, 'time');
+      GrJankDetector.jank = 42;
       element.beforeLocationChanged();
+      assert.equal(GrJankDetector.jank, 0);
+      assert.isTrue(element.reporter.calledWithExactly(
+          'lifecycle', 'UI Latency', 'Jank count', 42));
       assert.isTrue(element.time.calledWithExactly('DashboardDisplayed'));
       assert.isTrue(element.time.calledWithExactly('ChangeDisplayed'));
       assert.isTrue(element.time.calledWithExactly('DiffViewDisplayed'));
diff --git a/polygerrit-ui/app/test/index.html b/polygerrit-ui/app/test/index.html
index 6cf674a..6a562fc 100644
--- a/polygerrit-ui/app/test/index.html
+++ b/polygerrit-ui/app/test/index.html
@@ -88,6 +88,7 @@
     'core/gr-error-manager/gr-error-manager_test.html',
     'core/gr-main-header/gr-main-header_test.html',
     'core/gr-navigation/gr-navigation_test.html',
+    'core/gr-reporting/gr-jank-detector_test.html',
     'core/gr-reporting/gr-reporting_test.html',
     'core/gr-router/gr-router_test.html',
     'core/gr-search-bar/gr-search-bar_test.html',